And now it turns out that spend far more time caring for their aging parents as well. That’s the dismal conclusion of a research study presented this week at the annual meeting of the American Sociological Association, in San Francisco. If you look at husbands and wives alone, says study author Angelina Grigoryeva, a doctoral student at Princeton University, things look equal. “Each spouse,” she says, “tends to take care of his or her own parents.”

But elder care is more complicated than that, since siblings are also part of the equation. And when you factor them in, the picture becomes very different: her analysis, based on her analysis of the data rich University of Michigan Health and Retirement Study, shows that daughters give an average of 12.3 hours of elder care per month, while sons provide just 5.6. “The results,” she says, “suggest that daughters try to provide as much care as they can, while sons only step in when there’s nobody else to do it.”

It’s not necessarily that men are selfish jerks. “The difference between elder care and housework,” says Grigoryeva, “is that the former is very hands-on, and often requires intimacy, so mothers might tend to prefer to be helped by their daughters rather than their sons.” Since women outlive men, on average, and there are more female than male elders, that could contribute to the skewed statistics.

Grigoryeva also notes another difference between elder care and other forms of domestic chores: “For housework and childcare,” she says, “the gender gap is still there, but it has narrowed over time.” That’s not what she finds with elder care. “This suggests that there may be some cultural inertia involved. People talk a lot the gap in reference to housework and child care, but not so much about caring for the aging.”